A bearing assembly of this kind is known from U.S. Pat. No. 5,803,616, which discloses a double-row taper roller bearing suitable for railway applications in which a grease retainer is mounted to an outer ring of the bearing between the two rows of tapered rollers, at a small-diameter end of the rollers. In a tapered roller bearing, grease lubricant is urged from the small diameter end of the bearing to a large-diameter end under the action of centrifugal force. Therefore, grease that is initially provided between the two roller sets migrates relatively quickly to an axially outer side of the bearing, where the grease contributes little to the lubrication of the bearing. As a result, relubrication is required on a regular basis. Furthermore, the migration of the grease from the small diameter end to the large diameter end creates churning losses and friction.
The retainer disclosed in U.S. Pat. No. 5,803,616 has a ring-shaped channel which is axially delimited by two side walls of the retainer. The side walls have apertures for communicating the inner space of the channel with the bearing space. The grease retainer therefore allows some migration of grease to the bearing space but prevents the grease from migrating too quickly, even under the influence of centrifugal forces and shock loads experienced during operation. Retaining the grease therefore helps to increase relubrication intervals.
Grease retention is also a problem in bearing applications where the bearing has a vertical axis of rotation, such as, for example, the tail rotor bearing of a helicopter. A solution to this problem in a bearing of this kind is disclosed in U.S. Pat. No. 6,854,892. A swashplate assembly is described in which a rotating swashplate is supported relative to a stationary swashplate by means of a duplex bearing arrangement having a spacer arrangement between the two bearings. The spacer arrangement has a lubricant chamber, a first spacer element comprising a centrifugal ramp and a second spacer element comprising a baffle. The baffle divides the lubricant chamber into first and second chambers, with each chamber communicating with one of the bearings in the duplex arrangement. The centrifugal ramp counteracts the effects of gravity and uses centrifugal forces to ensure a supply of lubricant to the upper bearing of the arrangement.
There is still room for improvement.